The present invention is directed to chair with an automatic standing aid which can lift the operator into a standing position while he or she remains supported and also lower the operator back into a seated position. This function is referred to herein as a "stand-up" feature, and wheelchairs with such a feature are often referred to as "stand-up" wheelchairs.
The stand-up feature in the wheelchair provides the user with greater independence in that it enables him or her to do many activities within environments such as stores, residences, and places of work which cannot be done in the sitting position. This includes opening windows, removing objects from shelves, and operating appliances. Many other activities become more convenient with the greater field of view afforded by the standing position. Employment opportunities are broadened because many workplace modifications are no longer necessary where the wheelchair user has the ability to rise to a standing position. Money may be saved through less workplace and home modifications. Personal maintenance is also made easier for the wheelchair user in that dressing and personal hygiene are simplified. Social interaction is also improved with the stand-up feature in that the occupant may conduct eye-level conversions with companions, coworkers, merchants, etc. Many more leisure activities are possible and more enjoyable.
Standing has many physiological advantages for a person confined to a wheelchair, as well. It stimulates circulation, reduces bone decalcification and pressure sores, and helps with bladder training. Money may be saved with reduced health care and lower therapy costs.
Wheelchairs with a stand-up feature are known in the art and are commercially available. These wheelchairs must accommodate for the loss of the stability when these chairs are in the upright position. The stability of the wheelchair is reduced when the operator is lifted to the upright position because the center of gravity is raised and moved closer to the front axle. The stability of the stand-up wheelchair is defined as its ability to resist tipping over. The wheelchair may tip during a quick stop or start. Accordingly, some conventional stand-up wheelchairs do not move while the seat is in the upright position. Those wheelchairs which provide movement while the seat is in the upright position are large, very heavy, and require complex integration of the lift mechanism into its own heavy mobile power base to provide stability.
It is desirable to provide a wheelchair with a stand-up feature which is simple, light-weight and mobile in the upright position. It is also desirable to provide a chair with a lift mechanism for vertical support adaptable to existing mobile power bases which will enable motion in the upright position.